Fully-differential programmable gain amplifier

Abstract

A programmable a fully-differential programmable gain amplifier for reducing distortion, switching transients and interference, and improving bandwidth. In one embodiment, the amplifier includes a programmable gain module, an amplifier coupled to the current mode outputs and a data latch circuit of the programmable gain module, the amplifier configured to apply common mode voltage to the data latch circuit, and a current-to-voltage converter. In one embodiment, the fully-differential programmable gain amplifier controls distortion and switching interference during amplification by sensing common mode signals to produce an error signal, and applying the resulting error signal to the programmable gain module for multiplying digital to analog conversion. Components of the fully-differential programmable gain amplifier provide compensation of distortion caused by nonlinearity of device switches and switch resistance, and can include a floating supply, galvanic isolation of control signals and a common mode voltage controller.

What is claimed is: 
     
       1. A fully-differential programmable gain amplifier comprising:
 a first input; 
 a second input; 
 a first output; 
 a second output; 
 a programmable gain module coupled to the first input and the second input, the programmable gain module including
 a data latch circuit configured to
 control a first set of switches for a first resistive ladder network to provide output to a first current mode output, and 
 control a second set of switches for a second resistive ladder network to provide output to a second current mode output; 
 
 an amplifier coupled to the first current mode output, the second current mode output, and the data latch circuit, the amplifier configured to apply common mode voltage to the data latch circuit; and 
 a current-to-voltage converter coupled to the first current mode output, the second current mode output, the first output and the second output, the current-to-voltage converter configured to
 receive at least one output current mode signal from the first current mode output and the second current mode output, and 
 produce an output signal by converting differential input received from the at least one output current mode signal from the first current mode output and the second current mode output. 
 
 
 
     
     
       2. The fully-differential programmable gain amplifier of  claim 1 , wherein the programmable gain module is a dual multiplying digital to analog converter. 
     
     
       3. The fully-differential programmable gain amplifier of  claim 1 , wherein the programmable gain module includes
 the first resistive ladder network coupled to the first input, 
 the first set of switches for the first resistive ladder network, the first set of switches coupled to a first current mode output, 
 the second resistive ladder network coupled to the second input, and 
 the second set of switches for the first second ladder network, the second set of switches coupled to a second current mode output, 
 the data latch circuit configured to control the first set of switches for the first resistive ladder network to provide output to the first current mode output, and control the second set of switches for the second resistive ladder network to provide output to the second current mode output. 
 
     
     
       4. The fully-differential programmable gain amplifier of  claim 1 , wherein the programmable gain module receives control signals to adjust amplification of at least one signal received relative to the first input and second input signals. 
     
     
       5. The fully-differential programmable gain amplifier of  claim 1 , wherein the amplifier is a voltage follower with a positive input connected to a voltage ladder between the first current mode output and second current mode output, a negative input connected to an output of the voltage follower by a negative feedback loop and a floating ground supply of the programmable gain module. 
     
     
       6. The fully-differential programmable gain amplifier of  claim 1 , wherein the amplifier is a correction module configured to sense a common-mode signal between first current mode output and the second current mode output and to provide corrective feedback to the programmable gain module. 
     
     
       7. The fully-differential programmable gain amplifier of  claim 1 , wherein the current-to-voltage converter is differential module configured to produce a positive output signal to the first output and a negative output signal to the second output, wherein the first output and second output are opposite each other and equal in magnitude to a difference between the amplified first and second input signals. 
     
     
       8. The fully-differential programmable gain amplifier of  claim 1 , wherein the current-to-voltage converter includes a first output feedback loop coupled to the first output and an input of the current-to-voltage converter, and a second output feedback loop coupled to the second output and an another input of the current-to-voltage converter. 
     
     
       9. The fully-differential programmable gain amplifier of  claim 1 , further comprising a floating supply to power the programmable gain module. 
     
     
       10. The fully-differential programmable gain amplifier of  claim 1 , further comprising a galvanic isolator coupled to the programmable gain module, the galvanic isolator configured to block low voltage DC current to the programmable gain module. 
     
     
       11. A fully-differential programmable gain amplifier comprising:
 a first input; 
 a second input; 
 a first output; 
 a second output; 
 a programmable gain module coupled to the first input and the second input, the programmable gain module including
 a first resistive ladder network coupled to the first input, 
 a first set of switches for the first resistive ladder network, the first set of switches coupled to a first current mode output, 
 a second resistive ladder network coupled to the second input, 
 a second set of switches for the second resistive ladder network, the second set of switches coupled to a second current mode output, 
 a data latch circuit configured to
 control the first set of switches for the first resistive ladder network to provide output to the first current mode output, and 
 control the second set of switches for the second resistive ladder network to provide output to the second current mode output; 
 
 an amplifier coupled to the first current mode output, the second current mode output, and the data latch circuit, the amplifier configured to apply common mode voltage to the data latch circuit; and 
 a current-to-voltage converter coupled to the first current mode output, the second current mode output, the first output and the second output, the current-to-voltage converter configured to
 receive at least one output current mode signal from the first current mode output and the second current mode output, and 
 produce an output signal by converting differential input received from the at least one output current mode signal from the first current mode output and the second current mode output. 
 
 
 
     
     
       12. A method for a fully-differential programmable gain amplifier, the method comprising:
 receiving, by a programmable gain module of the fully-differential programmable gain amplifier, an input signal; 
 receiving, by the programmable gain module, a control signal; 
 supplying, by the programmable gain module, at least one output current mode signal from to first current mode output and to a second current mode output to provide a differential input signal, wherein output of the programmable gain module is in response to the control signal; 
 sensing, by an amplifier of the a fully-differential programmable gain amplifier, a common mode voltage to feed a common mode of the programmable gain module; and 
 producing, by a current-to-voltage converter of the fully-differential programmable gain amplifier, an output signal by converting the differential input signal to output an amplified input signal based on the control signal. 
 
     
     
       13. The method of  claim 12 , wherein the amplifier is configured as a voltage follower with a positive input connected to a voltage ladder between circuit paths of the amplified first and second input signals, a negative input connected to the voltage follower's output via a negative feedback loop, and output connected to the floating ground of the programmable gain module. 
     
     
       14. The method of  claim 12 , wherein a correction module senses the common-mode voltage between the amplified first and second input signals and sends corrective feedback to the programmable gain module. 
     
     
       15. The method of  claim 12 , wherein the correction module compensates for distortion caused by MOSFET switches of the fully-differential programmable gain module. 
     
     
       16. The fully-differential programmable gain amplifier of  claim 11 , wherein the programmable gain module receives control signals to adjust amplification of at least one signal received relative to first input and second input signals. 
     
     
       17. The fully-differential programmable gain amplifier of  claim 11 , wherein the amplifier is a voltage follower with a positive input connected to a voltage ladder between the first current mode output and second current mode output, a negative input connected to an output of the voltage follower by a negative feedback loop and a floating ground supply of the programmable gain module. 
     
     
       18. The fully-differential programmable gain amplifier of  claim 11 , wherein the amplifier is a correction module configured to sense a common-mode signal between the first current mode output and the second current mode output and to provide corrective feedback to the programmable gain module. 
     
     
       19. The method of  claim 12 , wherein the current-to-voltage converter with a first resistive feedback loop connecting a positive output signal path to an amplified first signal path and a second resistive feedback loop connecting a negative output signal path to an amplified second signal path. 
     
     
       20. The method of  claim 12 , wherein the fully-differential programmable gain amplifier is configured to control distortion and switching interference during amplification by
 sensing common mode voltage on outputs of a first current path and a second current path, 
 comparing common mode signal on the outputs of the first current path and a second current path with ground, 
 amplifying the common mode signal on the outputs of the first current path and the second current path with the ground to produce an error signal, and 
 applying the error signal to the programmable gain module for multiplying digital to analog conversion.